A description will now be given of problems of conventional transmission screens using various kinds of Fresnel lens means such as a refraction Fresnel lens plate, a total reflection Fresnel lens plate, and a refraction total reflection Fresnel lens plate by referring to FIG. 1 to FIG. 3.
FIG. 1 is a diagram showing a configuration and operation of a conventional refraction Fresnel lens plate. FIG. 1 shows a shape of a cross section of the conventional refraction Fresnel lens plate in which a refraction Fresnel plane is formed at an incident side of a projected light flux. In FIG. 1, reference character 110A is a refraction Fresnel lens plate (as refraction Fresnel lens means), reference number 111 denotes a refraction inclined plane (as a refraction Fresnel plane), 112 indicates an ineffective facet plane (as a refraction Fresnel plane), and 115 designates an outgoing plane. Reference character n designates a normal of the refraction Fresnel lens plate 110A (or the outgoing plane 115).
Reference number 150 designates a projected light flux of the refraction Fresnel lens plate 110A, 152 denotes an ineffective flux of light, 153 indicates an effective flux of light. The refraction Fresnel lens plate 110A comprises the refraction inclined plane 111 and the ineffective facet plane 112 adjacent to the plane 111, which are formed in a periodic structure.
Next, a description will now be given of the operation.
The projected light flux 150 enters in an angle to the normal n of the refraction Fresnel lens plate 110A. A part of the light flux 150 is refracted (in optical action) by the refraction inclined plane 111 toward the direction of the normal n, and outputs as an effective flux of light 153 from the outgoing plane 115 of the refraction Fresnel lens plate 110A.
On the other hand, the remaining part of the light flux 150 is refracted (in optical action) at the ineffective facet plane 112 and becomes ineffective flux of light 152.
The ineffective flux of light 152 inclines to the normal n, a part thereof outputs through the outgoing plane 115, and another part thereof is reflected at the outgoing plane 115. The ineffective flux of light 152 reflected at the outgoing plane 115 enters the refraction inclined plane 111 or the ineffective facet plane 112 again, which form the refraction Fresnel lens plate 110A. The refraction and the reflection of the ineffective flux of light 152 are repeated between the refraction inclined plane 111 or the ineffective facet plane 112 and the outgoing plane 115.
The effective flux of light 153 in the above light fluxes is a normal image light. The ineffective flux of light 152 causes the generation of a double image and a ghost image to display spots and line images at incorrect display positions.
FIG. 2 is a diagram showing the explanation of the structure and the operation of the conventional total reflection Fresnel lens plate. FIG. 2 shows the shape of the cross section of the total reflection Fresnel lens plate in which the total reflection Fresnel plane is formed at the incident side of the projected light flux. In FIG. 2, reference character 110B is the total reflection Fresnel lens plate (total reflection Fresnel lens means), reference number 113 denotes a total reflection inclined plane (total reflection Fresnel plane), 114 indicates a transmission inclined plane (total reflection Fresnel plane), 115 denotes an outgoing plane, and n indicates the normal of the total reflection Fresnel lens plate 110B (or the outgoing plane 115).
Reference number 150 designates a projected light flux to the total reflection Fresnel lens plate 110B, 151 denotes an effective flux of light, and 152 designates a deviated flux of light (as the ineffective flux of light).
The total reflection Fresnel lens plate 110B is made up of a combination of the total reflection inclined plane 113 and the transmission inclined plane 114 adjacent to the total reflection inclined plane 113 in a periodic structure.
Next, a description will now be given of the operation. The projected light flux 150 enters at an angle to the normal n of the total reflection Fresnel lens plate 110B, apart thereof is refracted (in optical action) and then reflected (in optical action) at the transmission inclined plate 114 toward the normal n at the total reflection inclined plane 113, and then outputs as the effective flux of light 151 through the outgoing plate 115 of the total reflection Fresnel lens plate 110B.
On the other hand, the remaining part of the projected light flux 150 becomes a deviated flux of light 152, not reflected at the total reflection inclined plane 113.
The deviated flux of light 152 is inclined in direction to the normal n. A part thereof is output through the outgoing plane 115, another part thereof is reflected at the outgoing plane 115. Then, the deviated flux of light 152 reflected at the outgoing plane 115 enters again into total reflection inclined plane 113 or the transmission inclined plane 114 which forms the total reflection Fresnel lens plate 110B.
The refraction and the reflection of the deviated flux of light 152 are repeated between the total reflection inclined plane 113 or the transmission inclined plane 114 and the outgoing plane 115.
The effective flux of light 151 in the above light fluxes is the normal image light. The deviated flux of light 152 causes the generation of a double image and a ghost image which display spots and line images at incorrect display positions.
FIG. 3 is a diagram showing a configuration and operation of a conventional refraction total reflection Fresnel lens plate. FIG. 3 shows the configuration of the refraction total reflection Fresnel lens plate in which both the refraction Fresnel plane and the total reflection Fresnel plane are formed at the incident plane of the projected light flux.
In FIG. 3, the same components of the configurations shown in FIG. 1 and FIG. 2 will be referred to with the same reference numbers and characters. In FIG. 3, reference character 110C designates the refraction total reflection Fresnel lens (refraction total reflection Fresnel lens means).
Next, a description will now be given of the operation.
The projected light flux 150 enters in an angle to the normal n of the refraction total reflection Fresnel lens plate 110C. The light flux refracted at the refraction inclined plane 111 becomes the effective flux of light 153 which travels toward the direction of the normal n. In addition, the light flux refracted (in optical action) at the transmission inclined plane 114 and then reflected (in optical action) at the total reflection inclined plane 113 becomes the effective flux light 151 which travels to the normal n.
On the other hand, a projected light flux 150 and a projected light flux 150, the former is refracted (in optical action) at the ineffective facet plane 112 and the latter is refracted (in optical action) and does not perform the total reflection at the total reflection inclined plane 113, become the ineffective flux of light (as a deviated flux of light) 152.
The ineffective flux of light 152 travels towards a direction inclined relative to the normal n, and a part thereof outputs through the outgoing plane 115, and another part is reflected at the outgoing plane 115.
The ineffective flux of light 152 reflected at the outgoing plane 115 enters again into the refraction inclined plane 111, the ineffective facet plane 112, the total reflection inclined plane 113, and the transmitting inclined plane 114 which form the refraction total reflection Fresnel lens plate 110C. The refraction and reflection are then performed for the ineffective flux of light 152 between the refraction inclined plane 111, the ineffective facet plane 112, the total reflection inclined plane 113, the transmission inclined plane 114, and the outgoing plane 115.
The effective fluxes of light 151 and 153 in the above light fluxes are the normal image light. The ineffective flux of light 152 often causes a double image and a ghost image which display a spot and a line image at positions different from the normal display position.
In the configuration of the conventional transmission screen, a lenticular lens plate (omitted from diagrams) is arranged at the outgoing plane 115 side of the Fresnel lens plate 110A, the total reflection Fresnel lens plate 110B, the refraction total reflection Fresnel lens plate 110C shown in FIG. 1 to FIG. 3 in order to control a geometric field angle in a horizontal direction and an up-and-down direction and to make the image.
Because the conventional transmission screen has the configuration described above which generates the effective flux light to contributes the display of the normal projected image, it is difficult in principle to avoid the generation of the ineffective flux of light which causes the phenomenon of a double image and a ghost image. Therefore the conventional transmission screen involves a problem in which the double image and the ghost image overlap the normal projected image. Because the generation of the double image and the ghost image deteriorates a high image quality in display, there is a demand to decrease the generation of the double image and the ghost image.
The present invention is provided to solve the above-described problems, and the object of the present invention is to provide a transmission screen with a high image quality capable of avoiding any generation of ineffective fluxes of light and displaying the normal projected image only using effective fluxes of light.
In addition, another object of the present invention is to provide a projection display device capable of eliminating any generation of a double image and a ghost image and of displaying the image with a high quality.